This invention relates to the use of certain hydroxylated metabolites and derivatives of doxazosin (4-amino-2-[4-(1,4-benzodioxan-2-carbonyl)-piperazin-1-yl]-6,7- dimethoxyquinazoline), and their pharmaceutically acceptable acid addition salts for retarding the development of arterial disease in mammals, and, more specifically, for suppressing lipid deposition and fibrosis in the development of atherosclerotic plaques and thus reducing atherosclerotic plaque involvement in mammals.
Atherosclerosis, a disease of the arteries, is recognized to be the leading cause of death in the United States and Western Europe. The pathological sequence leading to atherosclerosis and occlusive heart disease has been described in detail by Ross and Glomset in New England Journal of Medicine 295, 369-377 (1976). The earliest stage in this sequence is the formation of "fatty streaks" (plaques) in the carotid, coronary and cerebral arteries and in the aorta. These, in turn, give rise to development of the "fibrous plaque", which consists of accumulated intimal smooth muscle cells laden with lipid and surrounded by extracellular lipid, collagen, elastin and proteoglycans. The cells plus matrix form a fibrous cap that covers a deeper deposit of cell debris and more extracellular lipid. The lipid is primarily free and esterified cholesterol. The fibrous plaque forms slowly, and is likely in time to become calcified and necrotic, advancing to the "complicated lesion" which accounts for the arterial occlusion and tendency toward mural thrombosis and arterial muscular spasm that characterize advanced atherosclerosis.
Statistical evidence suggests that hyperlipidemia and hypertension are primary risk factors in causing atherosclerosis. Treatment of atherosclerosis is, therefore, approached by attempts to control hypertension and hyperlipidemia by dietary or pharmacological means. Some success has been achieved in reducing the incidence and severity of atherosclerosis by strict adherence to a prudent diet, by lowering plasma lipids with drugs or with ileal bypass surgery and by lowering systemic blood pressure with diet or drugs. However, coronary heart disease remains a threat, even to individuals striving to control their risk factors. It has been speculated that every individual in the United States has some degree of atherosclerosis. This fact, along with the high associated mortality and the inadequacy of the present treatment methods, establishes the need for anti-atherosclerotic agents.
Doxazosin, its pharmaceutically acceptable acid addition salts and the use of doxazosin and such salts as regulators of the cardiovascular system, particularly in the treatment of hypertension, are referred to in U.S. Pat. No. 4,188,390, which is assigned in common with the present invention. The use of doxazosin as an antiatherosclerosis agent is referred to in U.S. Pat. No. 4,758,569, also assigned in common with the present invention.
Elliot et al., Am. J. Cardio 59, p. 78G-81G (1987), refer to two hydroxylated metabolites of doxazosin, in particular, the 5'-hydroxy and 6'-hydroxy metabolites. S. F. Campbell, in U.K. Patent Application No. 8605551, published as GB 271997A on Sep. 10, 1986 and assigned in common with the present invention, refers to the 5'-, 6'-, 7'- and 8'- hydroxy derivatives of doxazosin and their use in the treatment of hypertension and congestive heart failure.
Doxazosin, an inhibitor of .alpha.-adrengic receptors, is effective in treating hypertension and in lowering serum lipid levels in mammals. The present inventors have found that doxazosin inhibits aortic lipid infiltration and fibrosis in cholesterol fed rabbits and that this effect is independent of the lowering of blood pressure or serum lipid levels. This independent inhibition of aortic lipid infiltration and fibrosis by doxazosin is believed to be caused by the anti-oxidant properties of certain hydroxylated metabolites of doxazosin, and, in particular, the ability of these metabolites to inhibit the oxidative uptake of low density lipoproteins (LDL) by macrophages.